1. Field of the Invention
The invention relates to a retractable rod assembly, more particularly to a retractable rod assembly having a positioning device that can securely retain outer and inner tubes in an extended state.
2. Description of the Related Art
Referring to FIGS. 1, 2 and 3, a conventional telescopic rod 10 is shown to comprise an inner tube 11, an outer tube 12 sleeved on the inner tube 11 and slidable along the length of the inner tube 11, and a positioning device 20 disposed in the inner tube 11. The inner tube 11 is formed with a radial positioning hole 111. The outer tube 12 is formed with a plurality of radial adjusting holes 121 that are spaced apart from each other along the length of the outer tube 12. The positioning device 20 includes a leaf spring 21 disposed in the inner tube 11, and a positioning button 22 mounted on one end of the leaf spring 21. The positioning button 22 extends out of the positioning hole 111 in the inner tube 11 and through one of the adjusting holes 121 in the outer tube 12. When adjusting the length of the telescopic rod 10, the positioning button 22 is first pushed against the biasing action of the leaf spring 21 such that the positioning button 22 ceases to extend into any of the adjusting holes 121 in the outer tube 12. Then, the outer tube 12 is slid relative to the inner tube 11 until a selected one of the adjusting holes 121 is aligned with the positioning hole 111. At this time, due to the resiliency of the leaf spring 21, the positioning button 22 will automatically extend through the selected adjusting hole 121 to retain the telescopic rod 10 at the desired length.
The following are some of the drawbacks of the conventional telescopic rod 10:
Due to manufacturing constraints, a little space is present between the inner tube 11 and the outer tube 12. Because positioning between the inner and outer tubes 11, 12 is achieved at a single point, wobbling between the inner and outer tubes 11, 12 easily occurs, which is worse when the telescopic rod 10 is relatively long.
Moreover, since the positioning button 22 projects through the outer tube 12, accidental pressing of the same is likely to occur. In the event that the positioning button 22 was accidentally pushed such that it is disengaged from the outer tube 12, undesired movement of the outer tube 12 relative to the inner tube 11 can occur.
Furthermore, the V-shaped leaf spring 21 easily suffers from elastic deformation, and the precision of positioning will decrease such that the service life of the positioning device 20 is accordingly relatively short.